Distance in EXIF

Started Aug 10, 2013 | Discussions thread
RS_RS Senior Member • Posts: 1,788
Re: Distance in EXIF

WilbaW wrote:

Severian The Lame wrote:

Focus zones differ by lens but there appears to be a limited number of zones that a lens reports or that the camera will record.

Apparently there is an encoder in each lens that captures the focus position using a certain number of bits. If you're seeing 31 zones that would be 5 bits. I've been told that typical zoom might have 8 discrete postions (3 bits).

That information would be pretty useless for autofocus (which is closed-loop anyway, so it's not needed), but apparently is useful for E-TTL II flash systems.

… and for aberration correction in DPP, where it is used to set the distance slider to optimise the correction for focus setting – again, an application where moderate precision is good enough.

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